This invention relates to fasteners for joining components, and in particular to a new and improved fastener suitable for use when components are to be jointed and disconnected rapidly while at the same time requiring relatively large forces for bringing the components together.
Fasteners for rapid fastening and release operations have been in use for a considerable period of time, especially in the aerospace industry. At the same time, it is desirable to avoid requiring any special tools for operating the fasteners, since these special tools must be available whenever and wherever access is required.
One fastener in general use today which avoids the time required for conventional screw fasteners and also special tool requirements is the quarter turn fastener which is widely used to replace common screws and bolts.
However, the quarter turn fastener does not have the capability of drawing structures or components together over separations of several inches, but is limited to small fractions of an inch. At the present time, threaded fasteners or elaborate latching mechanisms are used where the component spacing is in the order of inches. Large "V" bands currently used for securing sections of aircraft engines together require tightening through several inches into a preload of thousands of pounds and represent one application where a high speed fastener operable over a range of inches and capable of exerting high forces is required.
A special tool such as speed wrenches must be used for fastening with common threaded fasteners. Latching devices for such applications suffer from greater weight and size and also from the inability to provide accurate preloading on components being fastened.
Accordingly, it is an object of the present invention to provide a new and improved fastener which can operate at two speeds, with a fast speed low force portion for initially drawing the structures together and a slow speed high force portion for completing the closing.
Another object is to provide such a multiple speed fastener which operates in essentially the same manner as a common bolt, while requiring relatively few turns so that the fastener can be operated with an ordinary wrench.
A particular object of the invention is to provide such a multiple speed fastener which operates with a high pitch thread until a particular operating load is reached, and then automatically continues operating with a low pitch thread with increased mechanical advantage until the closing operation is completed.
Common fasteners with threads of differing pitches must be operated individually. To place two threads of differing pitch on a single shaft for threading into a receiving member of either pitch, or both pitches, would jam at the transition from one thread form to the other.
It is another object of the invention to provide a multiple speed fastener which achieves the transition from fast pitch to slow pitch without stripping threads or brinneling components or jamming.
Other objects, advantages, features and results will more fully appear in the course of the following description.